The objectives of this research are to purify and to characterize a natural protease inhibitor which can completely inhibit the primary processing of cowpea mosaic virus (CPMV) RNA in vitro protein synthesis products. Specifically, we plan to do the following experiments: (1) to develop a fractionation procedure for complete purification of the inhibitor molecule. (2) to biochemically characterize the inhibitor, including determination of basic chemical and physical properties, analysis of the reactivities of the inhibitor towards different proteases, and comparison of the activity of the inhibitor to the activities of chemically synthesized oligopeptides. (3) to examine the presence or absence of the inhibitor in CPMV-sensitive cowpea lines, and (4) to determine the amino acid sequence of the inhibitor through sequencing of cDNA or genomic DNA clones. Many animal and plant viruses use the method of proteolytic processing to produce functional proteins. For example, comoviruses, nepoviruse, potyviruses, picornaviruses, alphaviruses, flaviviruses, and retroviruses form all or most of their proteins by cleavage reactions. These viruses cause such acute or wide-spread diseases as polio, the common cold, hepatitis, encephalitis, yellow fever, and AIDS in humans, and severe diseases in important crop plants such as potato, soybean, and sugarcane. Obviously, methods for controlling the replication of these viruses have important implications in human health, medicine, and agriculture. Thus, our study on wheat embryo inhibitor, which represents a potential specific agent for blocking virus replication, should have significant meanings. To study the inhibitor, we will first need to purify this compound. After this is accomplished, we will then carry our experiments to determine basic structure and function properties of the inhibitor. The long term goal of this research is to use this inhibitor as a model for examining the possibility of controlling virus replication through inhibiting viral protein processing reactions.